Recommendations for quantitative uncertainty consideration in ecology and evolution.

Ecological and evolutionary studies are currently failing to achieve complete and consistent reporting of model-related uncertainty. We identify three key barriers - a focus on parameter-related uncertainty, obscure uncertainty metrics, and limited recognition of uncertainty propagation - which have led to gaps in uncertainty consideration. However, these gaps can be closed. We propose that uncertainty reporting in ecology and evolution can be improved through wider application of existing statistical solutions and by adopting good practice from other scientific fields. Our recommendations include greater consideration of input data and model structure uncertainties, field-specific uncertainty standards for methods and reporting, and increased uncertainty propagation through the use of hierarchical models.

Insights into the quantification and reporting of model-related uncertainty across different disciplines.

Quantifying uncertainty associated with our models is the only way we can express how much we know about any phenomenon. Incomplete consideration of model-based uncertainties can lead to overstated conclusions with real-world impacts in diverse spheres, including conservation, epidemiology, climate science, and policy. Despite these potentially damaging consequences, we still know little about how different fields quantify and report uncertainty. We introduce the "sources of uncertainty" framework, using it to conduct a systematic audit of model-related uncertainty quantification from seven scientific fields, spanning the biological, physical, and political sciences. Our interdisciplinary audit shows no field fully considers all possible sources of uncertainty, but each has its own best practices alongside shared outstanding challenges. We make ten easy-to-implement recommendations to improve the consistency, completeness, and clarity of reporting on model-related uncertainty. These recommendations serve as a guide to best practices across scientific fields and expand our toolbox for high-quality research.

Selective deep water coral bleaching occurs through depth isolation.

Climate change is degrading coral reefs around the world. Mass coral bleaching events have become more frequent in recent decades, leading to dramatic declines in coral cover. Mesophotic coral ecosystems (30-150 m depth) comprise an estimated 50-80 % of global coral reef area. The potential for these to act as refuges from climate change is unresolved. Here, we report three mesophotic-specific coral bleaching events in the northern Red Sea over the course of eight years. Over the last decade, faster temperature increases at mesophotic depths resulted in ~50 % decline in coral populations, while the adjacent shallow coral reefs remained intact. Further, community structure shifted from hard coral dominated to turf algae dominated throughout these recurrent bleaching events. Our results do not falsify the notion of the northern Red Sea as a thermal refuge for shallow coral reefs, but question the capacity of mesophotic ecosystems to act as a universal tropical refuge.

Ecosystem approach to harvesting in the Arctic: Walking the tightrope between exploitation and conservation in the Barents Sea.

Projecting the consequences of warming and sea-ice loss for Arctic marine food web and fisheries is challenging due to the intricate relationships between biology and ice. We used StrathE2EPolar, an end-to-end (microbes-to-megafauna) food web model incorporating ice-dependencies to simulate climate-fisheries interactions in the Barents Sea. The model was driven by output from the NEMO-MEDUSA earth system model, assuming RCP 8.5 atmospheric forcing. The Barents Sea was projected to be > 95% ice-free all year-round by the 2040s compared to > 50% in the 2010s, and approximately 2 °C warmer. Fisheries management reference points (FMSY and BMSY) for demersal fish (cod, haddock) were projected to increase by around 6%, indicating higher productivity. However, planktivorous fish (capelin, herring) reference points were projected to decrease by 15%, and upper trophic levels (birds, mammals) were strongly sensitive to planktivorous fish harvesting. The results indicate difficult trade-offs ahead, between harvesting and conservation of ecosystem structure and function.

Experimental evidence for reduced mortality of Agaricia lamarcki on a mesophotic reef.

Mesophotic Coral Ecosystems (MCEs) may act as a refuge for impacted shallow reefs as some of the stressors affecting tropical reefs attenuate with depth. A less impacted population at depth could provide recruits to recolonise shallow reefs. Recently, disturbance has been reported on several mesophotic reefs including storm damage, biological invasions, and coral bleaching; calling into question the extent of deep reef refuges. We report on a reciprocal transplant experiment between shallow and mesophotic reefs in the Caribbean, which occurred during a period of coral bleaching. 102 fragments of Agaricia lamarcki were collected down a continuous depth gradient at two sites to a maximum depth of 60m. Fragments were transplanted to either a shallow or mesophotic station at a third site, with controls. This allowed the disaggregation of the effect of the disturbance experienced during the observation period, and any potential acclimation resulting from the historical location of a fragment. Mortality and bleaching were quantitatively assessed. We found the relocation depth of a coral fragment had the strongest effect on both survival and the degree of bleaching recorded. The site a fragment was collected from, and the original collection depth, failed to explain mortality or bleaching with statistical significance. This experiment provides support for the assumption that mesophotic corals may be protected in comparison to shallow reefs, in spite of the potential effects of differing susceptibilities to stress.

Using light-dependent scleractinia to define the upper boundary of mesophotic coral ecosystems on the reefs of Utila, Honduras.

Shallow water zooxanthellate coral reefs grade into ecologically distinct mesophotic coral ecosystems (MCEs) deeper in the euphotic zone. MCEs are widely considered to start at an absolute depth limit of 30m deep, possibly failing to recognise that these are distinct ecological communities that may shift shallower or deeper depending on local environmental conditions. This study aimed to explore whether MCEs represent distinct biological communities, the upper boundary of which can be defined and whether the depth at which they occur may vary above or below 30m. Mixed-gas diving and closed-circuit rebreathers were used to quantitatively survey benthic communities across shallow to mesophotic reef gradients around the island of Utila, Honduras. Depths of up to 85m were sampled, covering the vertical range of the zooxanthellate corals around Utila. We investigate vertical reef zonation using a variety of ecological metrics to identify community shifts with depth, and the appropriateness of different metrics to define the upper MCE boundary. Patterns observed in scleractinian community composition varied between ordination analyses and approaches utilising biodiversity indices. Indices and richness approaches revealed vertical community transition was a gradation. Ordination approaches suggest the possibility of recognising two scleractinian assemblages. We could detect a mesophotic and shallow community while illustrating that belief in a static depth limit is biologically unjustified. The switch between these two communities occurred across bathymetric gradients as small as 10m and as large as 50m in depth. The difference between communities appears to be a loss of shallow specialists and increase in depth-generalist taxa. Therefore, it may be possible to define MCEs by a loss of shallow specialist species. To support a biological definition of mesophotic reefs, we advocate this analytical framework should be applied around the Caribbean and extended into other ocean basins where MCEs are present.